Aqara Smart Lock U400

Overview

The Aqara U400 is the first smart lock with UWB (Ultra Wideband) hands-free unlocking. Walk up to your door with your phone in your pocket and the lock opens before you touch the handle. No app, no fingerprint, no code. Consumer Reports said "this is the best experience I've ever had with a smart lock." 9to5Mac's reviewer said it unlocks before your hand even reaches the handle.

The U400 debuted at CES 2026 and started shipping in February. It uses the same UWB radio technology as Apple AirTags, but instead of finding your keys, it detects your phone's precise position and direction relative to the lock. The lock knows whether you're inside or outside, so it won't unlock when you walk past it in your hallway. HomeKit News called it "probably the best smart lock from any company I've reviewed so far."

It works with Apple Home Key, Matter over Thread, Alexa, Google Home, SmartThings, and Home Assistant. The big caveat: UWB hands-free unlocking currently requires an iPhone 11 or later (not SE or 16e) running iOS 18.5+ or an Apple Watch Series 6+ running watchOS 11.5+, plus a Thread-enabled Apple Home hub. Android UWB support is planned through the Aliro standard but hasn't launched yet.

Key Features

UWB is the headline. Unlike Bluetooth-based auto-unlock (which uses signal strength and can be fooled by relay attacks), UWB uses time-of-flight signals to measure precise distance and direction. The lock knows exactly where your phone is within inches. One AppleInsider reviewer found it unlocked reliably when their partner arrived home without any phone setup needed on the partner's device.

Beyond UWB, the U400 has six other unlock methods: NFC tap (Apple Home Key), fingerprint reader, keypad with up to 75 codes, physical key, voice assistants, and the Aqara app. It supports up to 100 users through Aqara with admin, standard, and temporary roles.

The lock runs on a 4,880 mAh rechargeable battery (USB-C) that lasts up to 6 months per charge. The battery is removable so you can charge it without taking the lock off the door. The exterior components are IP65 rated for weather resistance. It comes in Silver and Black.

Matter over Thread means it works across ecosystems without a proprietary hub. You can control it from Apple Home, Google Home, Alexa, SmartThings, or Home Assistant natively.

Performance

The UWB unlock works. Every major reviewer confirms this. Digital Reviews Network reported zero false positives or random unlocks across weeks of testing. The lock clicked green and opened as they walked up, with only a couple of instances where a phone in a back pocket needed repositioning.

The inside/outside detection is key. Earlier Bluetooth auto-unlock systems (like August's) would sometimes unlock when you walked past the door inside your house. The U400's UWB directional sensing solves this. Multiple reviewers specifically tested this and confirmed it works correctly.

The fingerprint reader is fast. The keypad works. The physical key backup is there if the battery dies. Every unlock method works as expected. Tom's Guide gave it strong marks across the board.

One Aqara Forum user who runs Home Assistant on Android bought the U400 specifically for its Matter support and was able to connect it directly to Home Assistant via third-party Matter configuration, bypassing the Aqara app entirely.

Build Quality & Design

The U400 is a standard deadbolt replacement. Installation takes about 30 minutes if you're replacing an existing deadbolt. The interior escutcheon is larger than some competitors due to the battery compartment, but reviewers say it looks clean and modern.

The ANSI/BHMA Grade 3 rating is the main concern. Grade 1 is commercial-grade, Grade 2 is residential heavy-duty, and Grade 3 is residential standard. The U400 is Grade 3, which means it's fine for most homes but isn't the pick if physical security is your top priority. The Yale Assure Lock 2 and Schlage Encode Plus are both Grade 2.

The USB-C rechargeable battery is a nice upgrade over AA batteries that most smart locks use. Six months per charge is realistic based on early owner reports, and you can charge the battery separately without removing the lock.

Value for Money

The U400 is priced competitively for a UWB smart lock since it's the only one on the market right now. Compared to the Yale Assure Lock 2 or the Schlage Encode Plus (both around the same price but without UWB), the Aqara gives you the most advanced unlock technology available.

The Kwikset Aura Reach, which is in our database, is a Matter lock at a lower price point but lacks UWB, fingerprint, and Apple Home Key. If you want basic smart lock functionality for less, it works. If you want the walk-up-and-it-opens experience, the U400 is the only option.

Who Should Buy This

Apple ecosystem users. The UWB unlock with iPhone and Apple Watch is the killer feature, and it requires Apple hardware to work right now. If your household uses iPhones, this is a no-brainer upgrade from any other smart lock.

Smart home enthusiasts who want Matter-native devices. The U400 works across every major platform without needing a proprietary hub.

Anyone tired of fumbling with keys, apps, or fingerprint readers when their hands are full. The walk-up unlock genuinely solves this problem.

Who Should Skip This

Android users, for now. UWB unlock requires Apple devices until Aliro support launches on Android. You can still use the fingerprint reader, keypad, and app, but you'd be missing the main selling point.

If physical security rating matters to you, the Grade 3 ANSI/BHMA rating is below the Grade 2 locks from Yale and Schlage. For most residential use this is fine, but if you want the strongest physical lock, look elsewhere.

If you have an older home with a non-standard door prep, check compatibility. The U400 fits standard deadbolt cutouts but some vintage doors may need modification.